Left handed drill bit? I’ve just bit the bullet in the past and replace the flipper bat and spring, along with getting a crank.

Easy out. Sometimes had luck with cutting a slot in what's left of the screw with a Dremel cutoff wheel. Then you can use a small straight slot screwdriver to unscrew it.

or a hacksaw to cut off the shaft

But that still doesn't get the broken screw out of a pawl that is no longer available (no reproductions).

If the good screw is out or loose, you may be able to hold the bat on the topside and the paw ul on the underside. Twist and pull apart.
Then the broken screw may be easier to move with ez out or drill bit.

Id try using a dremmel to cut a slot in what's left of the old screw in hopes it could be removed with a flat head driver.

A bit of it is sticking out. You could try vise grips or Vampliers.

saw a whole bunch at the show today...

Right side crank arms are still available - left side are not, but you can substitute the earlier Gottlieb flipper generation crank arm, which is a similar design and still available, to make it work. This is a right side crank arm that the OP is looking at it, so should be no problem getting a new one if needed.